Assessment of the Biyadh groundwater quality and geochemical process in Saudi Arabia using statistical, modelling, and WQI methods

This research aimed to understand the variations in the groundwater quality and hydrochemical processes in the Biyadh aquifers in central Saudi Arabia. The Biyadh Aquifer in the Riyadh area is the primary natural water resource for Wadi Sahba and Wasia Well Fields. The present study collected thirty groundwater samples from the Biyadh aquifer in the outcrop and confined parts. The samples were evaluated by multivariate statistical methods and hydrochemical modelling to understand the geochemical processes that control the groundwater. Also, it used various indexes to find the groundwater's suitability for drinking, agricultural, and industrial purposes. The analysis revealed a general evolution in groundwater quality as groundwater flowed east and northeast. The TDS increases from 1730 mg/l in WS to 2370 mg/l in WWF. The groundwater facies developed from Ca-Mg-SO4-Cl to Ca-Na-Mg-SO4-Cl in WS and ended with Ca-Na-SO4-Cl in WWF. Applying Pearson's correlation matrix, cluster analyses, and factor analyses indicate that the ions significantly influence groundwater mineralization. The geochemical modelling revealed that the dissolution of the calcite, halite, anhydrite, and gypsum minerals increases with the direction of groundwater flow. In addition, the agriculture activities in Wadi Sahba mixed with irrigation return water to groundwater and increase nitrate (NO3) concentration. Biyadh groundwater has a better quality for drinking in the confined aquifer than in the unconfined aquifer, and both areas are suitable for irrigation. The TH indicates that the groundwater becomes more suitable for industrial purposes as it flows toward the confined part of the aquifer.